Mechanistic insights into the oxidative coupling of N-heterocyclic carbenes within the coordination sphere of copper complexes.

The behavior of N-heterocyclic carbene (NHC) ligands in organometallic chemistry is hugely important for catalysis, due to the effect of these ligands on catalytic pathways and their involvement in catalyst decomposition. In this report, a combined experimental and computational study is presented, which provides mechanistic understanding of the unprecedented oxidative coupling of NHCs at Cu. The presence of Cu(I) -, Cu(II) -, and Cu(III) -NHC complexes during the process is postulated, with the unusual Ccarbene -Ccarbene oxidative coupling reaction occurring under extremely mild reaction conditions. This process may represent a novel pathway for the decomposition of Cu-NHC complexes.